President Barack Obama is showing solidarity with workers on Labor Day by signing an executive order Monday requiring paid sick leave for employees of federal contractors.

The White House says 300,000 of those workers will be getting the benefit for the first time.

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Obama will address the executive order at a major union rally and breakfast Monday in Boston.

The White House wouldn't specify the cost to federal contractors to implement the executive order. The Labor Department says any costs would be offset by savings that contractors would see from lower attrition rates and increased worker loyalty, but provided no details to back that up.

Contract workers will get a minimum of one hour of paid leave for every 30 hours they work. That's up to seven days per year.